Some 60,000 Twitter accounts have been set up by IS sympathisers since May, a Sky News investigation has found.

And despite the site vowing to stamp them out in the wake of the murder of James Foley, 27,000 continue to express pro-jihadi views.

In the 24 hours following the publication on Tuesday night of a video showing the murder of Steven Sotloff, 10% of all references to the video on the microblogging site were found to be positive.

In the first research of its kind, a unique analysis of the way Muslim extremists are using social media suggests sites are struggling to police postings effectively.

After Mr Foley's murder, Twitter announced it would suspend accounts that posted graphic imagery or "calls to violent actions".

Yet the analysis suggests that often as soon as an account is closed down, another replaces it almost instantly - with a simple change of name.

One account identified by the researchers posted a death threat to a journalist, was shut down and within days an account bearing a very similar name was positing similar material.

Twitter launched a crackdown last month

Another account found by the researchers was shut down, set up again under an almost identical name, posted explicit pictures of dead bodies apparently from the current conflict, was suspended again and then re-emerged under another identity.

The Sky News investigation found that these new accounts are then promoted by other IS-related Twitter accounts.

Video:What Are The Options To Stop IS?

In this way, the IS supporters are able to circumvent the ongoing efforts to remove them from Twitter.

The social media analysis was carried out on behalf of Sky News by the web intelligence firm Recorded Future.

As part of the research, analysts defined a pro-IS account as one talking about positively about IS and about violence.

Video:Public Views On Action To Stop IS

The research found that since May, Twitter has proved the most popular source for pro-IS tweets - where users are promoting either material sourced from Twitter or other Twitter accounts.

Staffan Truve, the chief technology officer of Recorded Future, said: "Clearly, the current manual process where Twitter shuts down accounts that are reported cannot keep up with this tactic.

"We believe automated approaches that use techniques similar to those we have presented here sentiment and network link analysis can be used to successfully block improper content that violates the Twitter rules."

Twitter declined to comment on the research.

Sky News spoke to one of the most prolific IS tweeters via Skype, whose accounts have twice been removed from Twitter but who is still tweeting.

He said he was a 19-year-old living in Western Europe and was proud of his contribution to the Islamic State.

"The reason I started tweeting was to support the mujahideen by activism," he said.